A bacterium against the tiger: preliminary evidence of fertility reduction after release of Aedes albopictus males with manipulated Wolbachia infection in an Italian urban area

BACKGROUND: Novel tools are needed to reduce nuisance and risk of exotic arbovirus transmission associated with the colonization of temperate regions by Aedes albopictus. Incompatible Insect Technique (IIT) is a population suppression approach based on cytoplasmic incompatibility between males with manipulated endosymbionts and wild females. Here we present the results of the first field experiment in Europe to assess the capacity of an Ae. albopictus line (ARwP) deprived of its natural endosymbiont Wolbachia and transinfected with a Wolbachia strain from the mosquito Culex pipiens - to sterilize wild females. RESULTS. We released ~4,500 ARwPmales weekly for 6 weeks in a green area within urban Rome (Italy) and carried out egg (N=13,442), female (N=128) and male (N=352) collections. Egg(N=13,783) and female (N=48) collections were also carried out in two untreated Control Sites. The percentage of viable eggs during releases was on average significantly lower in Treated than in Control Sites, with the highest difference (16%) after the fourth release. The ARwP/wild male ratio in the release spots between day-3 from the first ARwP male release and day-7 after the last release was on average 7:10. Released males survived up to two weeks. About 30% of the females collected in the release spots showed 100% sterility and 20% a strongly reduced fertility compared to Control Sites. CONCLUSIONS. Results support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context and stress the need of larger field trials to evaluate the cost-efficacy of the approach in suppressing wild populations.